diff --git a/src/minivhd.h b/src/minivhd.h
index a81cdf8..b01128c 100644
--- a/src/minivhd.h
+++ b/src/minivhd.h
@@ -121,15 +121,15 @@ void mvhd_close(MVHDMeta* vhdm);
  * 
  * Note, maximum VHD size (in bytes) is 65535 * 16 * 255 * 512, which is 127GB
  * 
- * This function determines the appropriate CHS geometry from a provided size in MB.
+ * This function determines the appropriate CHS geometry from a provided size in bytes.
  * The calculations used are those provided in "Appendix: CHS Calculation" from the document 
  * "Virtual Hard Disk Image Format Specification" provided by Microsoft.
  * 
- * \param [in] size_mb the desired VHD image size, in MiB
+ * \param [in] size the desired VHD image size, in bytes
  * 
  * \return MVHDGeom the calculated geometry. This can be used in the appropriate create functions.
  */
-MVHDGeom mvhd_calculate_geometry(int size_mb);
+MVHDGeom mvhd_calculate_geometry(uint64_t size);
 
 /**
  * \brief Read sectors from VHD file
diff --git a/src/minivhd_manage.c b/src/minivhd_manage.c
index 3d79f25..9569054 100644
--- a/src/minivhd_manage.c
+++ b/src/minivhd_manage.c
@@ -327,9 +327,9 @@ bool mvhd_file_is_vhd(FILE* f) {
     }
 }
 
-MVHDGeom mvhd_calculate_geometry(int size_mb) {
+MVHDGeom mvhd_calculate_geometry(uint64_t size) {
     MVHDGeom chs;
-    uint32_t ts = ((uint64_t)size_mb * 1024 * 1024) / MVHD_SECTOR_SIZE;
+    uint32_t ts = size / MVHD_SECTOR_SIZE;
     uint32_t spt, heads, cyl, cth;
     if (ts > 65535 * 16 * 255) {
         ts = 65535 * 16 * 255;
diff --git a/test_program/minivhd_test.c b/test_program/minivhd_test.c
index ca70ecd..92dceee 100644
--- a/test_program/minivhd_test.c
+++ b/test_program/minivhd_test.c
@@ -12,7 +12,7 @@ int main(int argc, char* argv[]) {
     MVHDMeta* vhdm = mvhd_open(path, false, &err);
     mvhd_close(vhdm);
     /* Creation Tests */
-    MVHDGeom geom = mvhd_calculate_geometry(512);
+    MVHDGeom geom = mvhd_calculate_geometry(512 * 1024 * 1024);
     vhdm = mvhd_create_sparse("C:/StandaloneProg/pcem/Images/minivhd/sparse.vhd", geom, &err);
     if (vhdm == NULL) {
         printf("Failed with exit code: %d", err);